New Outlook error "Can't attach files across accounts" since Windows update

Hi @Weis Mateen, 

Thank you for posting your question in the Microsoft Q&A forum. After carefully reviewing your scenario, I ran a test in my own environment and received a similar message:  "Can't attach files across accounts." 

Upon further research, I found that the New Outlook client currently does not support drag-and-drop of emails or attachments between different accounts or mailboxes (e.g., from a shared mailbox to a personal one). This is due to current design limitations in the New Outlook, which does not yet offer the same level of flexibility as the classic Outlook desktop app.  Similarly, Outlook on the web (OWA) in Microsoft Edge also has this limitation: drag-and-drop actions are only supported within the same mailbox. 

That said, many users have reported this issue, and Microsoft is actively working to improve the experience.  According to: https://www.microsoft.com/en-US/microsoft-365/roadmap?filters=&searchterms=493289 , a new drag-and-drop capability is being rolled out for the New Outlook client. This feature will allow users to move emails and files between accounts as attachments. The rollout began in August 2025, and the feature is expected to become more widely available soon. 

Note: The Microsoft 365 Roadmap is an official platform where you can track upcoming features, improvements, and release timelines across Microsoft products. 

I completely understand that this limitation may cause inconvenience in your workflow. As a forum moderator, my role is to assist based on publicly available documentation, product research, and community experience. While I don’t have the ability to escalate product issues directly, I’ve done my best to gather and share relevant information that may help clarify the situation.  

If you find this response helpful in understanding the current product behavior and available updates, I’d truly appreciate it if you could consider marking it as the Accepted Answer. This will help pin the post to the top, making it easier for others in the community who may be facing the same issue to discover the helpful information and benefit from the insights shared. 

Thank you again for your understanding! 

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